Subject: Re: Limiting the advertised MSS, again.
To: Rick Byers <>
From: None <>
List: tech-net
Date: 12/07/2001 10:54:34
In message <Pine.NEB.4.33.0112062151470.3863-100000@Apenheul.BigScaryChildren.n
et>Rick Byers writes:
>Someone mentioned that lowering the MTU on a route should cause the
>TCP MSS to get lowered correspondingly.  I thought it was working, but I
>must have been drunk or something, because the per-route MTU doesn't seem
>to affect the advertised MSS at all (which I should have known since I've
>was staring at the tcp_mss_to_advertise code).
>Anyway, I know some people belive we shouldn't provide an option to cope
>with broken networks, but I believe the situation is already desperate
>enough that there is nothing to be gained by holding this feature back.
>Does anyone else think there should be a sysctl for lowering the MSS, or
>is there some better way?

I thought that your earlier patch looked fine.  I kinda liked the name
that jhawk suggested, maxmss, but that doesn't really seem important.
Having a way to lower the advertised MSS doesn't seem like the end
of the world.  It certainly doesn't violate the end-to-end principle 
the way that MSS-clamping does.  (And even that is not the end of the 
world, I guess, given NAT and all the rest of the evil out there.)  

I don't have the problem, so it is easy for me to get on my high horse.